A report by charities Inquest and Barrow Cadbury Trust that analyses the circumstances behind the deaths of 65 children, young people and young adults in custody in the 48 months between January 2011 and December 2014 found 54 were classified as self-inflicted.
Around one third of those who died had been in care or lived away from their family; 70 per cent had mental health conditions; nearly a quarter had a learning disability; and 34 per cent substance misuse problems.
The report, Stolen Lives and Missed Opportunities: The Deaths of Young Adults and Children in Prison, calls for an overhaul of the treatment of young offenders in the secure estate, particularly the most vulnerable with experience of being in care or having mental health problems.
Among key recommendations is a dramatic reduction in custodial sentences, which should only be used as a last resort. Where custody is used it should be in smaller prison units, with a focus on therapeutic support.
In addition, some secure estate funding should be diverted towards crime prevention and a greater focus on community support for those convicted of minor offences and who have mental health problems and substance abuse issues.
Deborah Coles, co-director of Inquest, said: “These deaths are the most extreme outcome of a system that fails some of society’s most disadvantaged children and young people.
“The number of deaths is high because prison is overused as the societal solution to a range of social problems that need to be addressed elsewhere. Many young people were failed by a range of social and welfare services well before they entered custody.
“Unless we radically rethink the way in which we respond to young people in conflict with the law the deaths will continue to shame our prison system and society.”
The report also calls for better training among staff in the secure estate in recognising and supporting vulnerable young offenders, who may be self-harming or have experiences of trauma in their life.
A greater crackdown on bullying is also needed as is a focus on targeting support at vulnerable young offenders during their first weeks in custody.
Where there has been a death of a young person in custody, families should automatically qualify for free legal representation at inquests says the report, which also criticises an inquest process that is beset with delays. Research found that a quarter of death in custody inquests carried out between August 2010 and January 2011 took more than two years to complete.
Sara Llewellin, chief executive of Barrow Cadbury Trust, added: “This report provides a particularly tragic window to see what is now irrefutable – a distinct approach to young adults at all stages of the criminal justice process would save young people’s lives, reduce future crime and prevent considerable economic waste.”
Of the 65 deaths over the four years, 62 were aged between 18 and 24, two were 17 and one was 15.
In addition, 14 were in young offender institutions (YOI) and 23 were in mixed prisons that accommodate both young and adult offenders. The highest number of deaths occurred in Glen Parva YOI (six) and Chelmsford prison (four).
Latest Youth Justice Board figures released in January showed the number of self-harm reports among per 100 young offenders in custody increased from 5.2 in 2012/13 to 6.6 in 2013/14.
Last month, a Howard League for Penal Reform report found that custody also damages young offenders' sexual development.